In this paper we briefly describe the main features of the CDF Silicon Vertex Detector (SVX) and discuss its performance during actual colliding beam operation at the Fermilab Tevatron. Details on S/N ratio, alignment, resolution, and efficiency are given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87708/2/1908_1.pd

Amidei, Dan

Azzi, P.

Bacchetta, N.

Bailey, M. W.

Barnett, B.A.

Bedeschi, F.

Bisello, D.

Bolognesi, V.

Boswell, C.

Busetto, G.

Carithers, W. C.

Carter, H.

Castro, A.

Dell’Agnello, S.

Derwent, P. F.

Dunn, A.

Ely, R.

Flaugher, B.

Galeotti, S.

Garfinkel, A. F.

Gold, M.

Grieco, G.

Haber, C.

Holland, S.

Kleinfelder, S.

Kruse, M. C.

Loreti, M.

Mariotti, M.

Matthews, J.

Menzione, A.

Merrick, T.

Nelson, C.

Pescara, L.

Punzi, G.

Raffaelli, F.

Ristori, L.

Schneider, O.

Segler, S.

Shaw, N. M.

Shaw, T.

Skarha, J. E.

Snider, F. D.

Song, T. Y.

Spies, A.

Tartarelli, F.

Tipton, P.

Tkaczyk, S.

Tseng, J.

Turini, N.

Turner, K.

Vejcik, Steve

Watts, G.

Wenzel, H.

Wesson, T. R.

Wester, W.

Wong, M.

Yao, W.

Zetti, F.

Describes the main features of the CDF Silicon Vertex Detector (SVX) and discuss its performance during actual colliding beam operation at the Fermilab Tevatron. Details on S/N ratio, alignment, resolution and efficiency are given

Dell`Agnello, S.

Barnett, B.

Skarha, J.

Vejcik, S.

Amidei, D.

UNT Digital Library

% @ FNAL/C--92/263-EFermi National Accelerator Laboratory _93oo,4,4:1.:I.FERMII_,AB-Conf.92/2t_EOperation of the CDF Silicon Vertex Detectorwith Colliding Beams at FermilabF. Bedeschi et al • .-_"..,C" [ _ '-"'; Fermi National Accelerator Laboratory _' jP.O. Box 500, Batavia, Illinois 60510 " /U92.'_--October 1992r, High Energy Physics,Published Proceedings XXVIth International ,.,onference onDallas, Texas, August 6-12, 1992MASTERI_l Operated by Univer_lies Research Association Inc.under Contract No. DE-ACO2-T6CHO3(XX) with the United States Departm_t of Energy ........,_,,_,._.....,_,_.__,,_,;._.. ... :.;_.,,_i....t..ji"._L.,,,iiic _,:.'_C'IPI ," ,I,,_,,,1111!' _rIi,r',,,,rlIFIT,Bp"'J,$DisclaimerThis report was prepared as an account of work sponsored by an agency of the United StatesGovernment. Neither the United States Government nor any agency thereof, nor any oftheir employees, makes any warranty, express or implied, or assumes any legal liability orresponsibility for the accuracy, completeness, or usefulness of any information, apparatus,product, or process disclosed, or represents that its use would not infringe privately ownedrights. Reference herein to any specific commercial product, process, or service by tradename, trademark, manufacturer, or otherwise, does not necessarily constitute or imply itsendorsement, recommendation, or favoring by the United States Government or anyagency thereof. The views and opinions of authors expressed herein do not necessarily stateor reflect those of the United States Government or any agency thereof.CDF, PLB,. SEC VTX, PL!BL/:C/J.d_.bFERM[LAB-CONF-92 /263-g' OPERATION OF THE CDF SILICON VERTEX DETECTORWITH COLLIDING BEAMS AT FERMILABF. Bedeschi, V. Bolognesi, S. Dell'Agnello, S. Galeotti, G. Grieco, M Mariotti,A. Menzione, G. Punzi, F. Raffaelli, L. Ristori, F. Tartarelli, N. Turini,H. Wenzel, F. ZettiINFN, University and Scuola Normale Superiore of Pisa, Pisa, Italy, 1-56100NI. W. Bailey, A. F. Garfinkel, M. C. Kruse, N. M. ShawPurdue University, West Lafayette, Indiana, 47907W. C. Carithers, R. Ely, C. Haber, S. Holland, S. Kleinfelder,T. Merrick, O. Schneider, W. Wester, M. Wong, W. YaoLawrence Berkeley Laboratory, Berkeley, California, 94720H. Carter, B. Flaugher, C. Nelson, S. Segler, T. Shaw,S. Tkaczyk, K. Turner, T. R. WessonFermi National Accelerator Laboratory, Batavia, Illinois, 60510B. Barnett, C. Boswell, J. Skarha, F. D. Snider, A. Spies,J. Tseng, S. VejcikThe John Hopkins University, Baltimore, M_yland, 21218D. Amidei, P. F. Derwent, T. Y. Song, A. DunnUniversity of Michigan, Ann ._rbor, Michigan, 48109M. Gold, J. Matthews, N. BacchettaUniversity of New Mexico, Albuquerque, New Mexico, 87131,P. Azzi, D. Bisello, G. Busetto, A. Castro, M. Loreti, L. PescaraUniversity of Padova, Padova, Italy, 1-35100P. Tipton, G. WattsUniversity of Rochester, Rochester, New York, 14627" Abstract "In this paper we briefly describe the main features of the CDF Silicon VertexDetector (SVX) and discuss its performance during actual colliding beam op-eration at the Fermilab Tevatron. Details on S/N ratio, alignment, resolutionand efficiency are given.INTRODUCTIONcrostrip detector (SVX) to provide high reso-The Collider Detector at Fermilab (CDF) lution tracking in the interaction region. This- is a multipurpose detector designed and built detector will allow us to resolve secondary ver-to study p/5 interactions at x/s = 2 TeV 1. Sev- tices from the decay of heavy-flavoured parti-aral upgrades have been added to the basic cles, with lifetimesintherangeoflO-la-lO -12detector for the data taking run which h_ re- seconds. We expect the SVX to give a fun-cently started; among these is a silicon mi- damental contribution to the measurement ofPublished Proceedings XXVIth International Conference on High Energy Physics,Dallas, TX, August 6-12, 1992.Him " "' "11'1 . _r,,ii llr_', I1'Pthe properties of the particles containing the b "quark and to the identification of events con-taining the top quark, if its production ratesare sufficiently high to _,llow detection.Several technical papers have been pre-sented in the past describing the SVX 2'4's'z,its front-end electronics 1°'11, the details of theconstruction s'8, the performance of prototypesduringbeam tests3'9,and the data acquisitionsystem12'13; in the following we will give onlya brief description of the detector and thenconcentrate on how the full detector performsduring actualdata takingconditionsat CDF,based on the informationextractedfrom thefirst few months of data collection. \_\THE SVX DETECTORThe SVX is installed surrounding the CDFinteraction region inside the vertex time pro-jec_ionchamber (VTX) and the centraltrack- Figurei.SchematicviewofoneSVX barr,.l,showinging chamber (CTC), One of itsmost distinc- the internalgeometry.fivefeaturesisitslength:over 50 cm dividedin two longitudinalsections(barrels)which levelcan be achieved.sitsymmetricallyabout the average interac-The main geometricalparameters of thetion point. This length is driven by the needSVX are the following: inner radius 2.99 ca,for a reasonably good acceptance in spite ofouter radius 7.85 ca, strip pitch 60/_m for thethe rather long size (Gaussian distributed withthe inner 3 layers and 55 #m for the outer one.cr = 35crn) of the Tevatron luminous region . A total of 288 single-sided microstrip detectorsEach barrel (Figure 1) is divided into 12 sec- are assembled into the system for a total oftions (wedges) which subtend 300 in azimuth. 46080 readout channels.Each wedge consists of 4 layers of silicon detec-An effective chilled-water cooling s systemtor modules (ladders) with silicon microstrips keeps the temperature of the detector in therunning parallel to the beam a,xis. To cope 20 - 25 °C range with a good safety margin.with the rather long length of the ladders with-out the number of readout channelsgetting DETECTOR CHARACTERIZATIONout of control,three 8.5 cm long microstripdetectors are assembled on each ladder, their Special calibration runs are taken periodi-strips wirebonded between adjacent detectors, cally betwe.en pp data-taking to monitor detec-with a single ceramic readout hybrid circuit tor performance and calculate constants to beboard (ear card) at one end. This configura- used later on in the data analysis. In partic-tion causes a pretty high capacitive load on the ular we monitor the pedestal distribution, theinputs to the front end electronics (,-, 30pF), gain and the sparsification thresholds for eachstill,as we shallsee,a quitereasonablenoise channel.The results,afterabout 2 months ofrunning, appear remarkably stable with time.The average noise measured is 12 ADC counts,equivalent to about 2000 electrons. This noise I Lo,,is very uniform, within a few ADC counts, ,60_- t,,o_ ,,:_across the whole detector. A uniformity well [ n l o_s 68,,within 5% is also observed for the gains. Some- ,,o _-what less.satisfactory is the threshold unifor- ,_0_-mity for a few wedges. Since we have only two [threshold setting lines per wedge, one for layer ,oo1 and olle for layers 2, 3 and 4, this results ina higher number of channels being read out in 8oa given wedge, if we want to preserve a good 60emciency for ali of the channels. Currentlythe typical fraction of channels being read out ,0per wedge is less than 5%, and about 15°70for 20[a couple of wedges. Still this is of no conse-, , ._ _ . , . I , ,,.I .U ,. i ._r,_-_-_%i "T_,---_--_'-quence to the quality of the data. o o _o ,oc ,_o 2oo 2_o 3oo 3_o ,oo ,_o _ooThe number of channels in the detector c,o,_.0,,,,,0._,._which do not respond properly (bad channels)is also monitored constantly. The fraction ofbad channels is about 1%, these channels being Figure 2. Charge distribution on layer 1 normalizedmostly either disconnected due to high strip to normalincidence (ADC counts).currents, or low gain or high noise. This frac-tion has been rather stable over a period oftime of several months. Alaxge number of the ergy release of charged particles in the indi-bad channels found had already been detected vidual SVX layers. This selection allows veryduring initial ladder testing, before the detec- good noise rejection and the normalization ofthe collected charge to normal incidence an-tor was assembled, gle. A typical distribution, quite consistentwith a Landau shape_ is shown in figure 2.RESULTS WITH TRACKSThe most probable value of this distributionAt present tracks in the SVX are found is about 110 ADC counts, corresponding to aonly as extrapolations of CTC tracks. The worst case S/N of 9 to 1.algorithm used associates one SVX point at a The efficiencies of the individual layerstime to an existing CTC track. At each iter- have been estimated by selecting all tracksation a new fit of the track is made, multiple with hits in the same wedge and then calcu-Coulomb scattering contributions axe included lating the ratio between the number of tracks: and a new (narrower) search road is estimated which miss a given layer, NI, and the sum. ofto search for hits in. the next layer. The al- N1 and the number of ali 4-hit tracks. Thisgorithm works its way from the outer to the procedure is quite safe for the two interme-inner layer. In the end only tracks with 3 or diate layers, since the presence of hits on themore SVX hits are saved, first and last layer protects us from acceptanceWe have used the charge associated with problems. The inef_ciency obtained this wayhits connected to 4-hit tracks to study the en- is about 3% for layers 2 and 3 of baxrel 0 and4% for layers 2 and 3 of barrel 1. These ineffi-ciencies are higher than those measured in thetestbeam 3'9 and possibly connected with the xb.om,,zsparsificationthresholdsettings Work how-ever isstillin progresson the optimizationof {o,2thesesettingsand thesenumbers may stillim- "prove In any case,due to the intrinsicredun- 00adancy of a 4-layer system, we still expect anoveralltrackingefficiencyof _99% with the oo4 •• . . : . ".• . " ' ", ', ..'.,,. ,_ ." V" " _" _.detector as it is, if we exclude acceptance ef- o [ • . ,,':, _". ,,'..-_,_._:_,_._'-:---l "' ' "" .t .i,,,. *° -, • '% "- ," •• .. ",. • ,.. ',**t ,'; ,f. :o_2"_ .......'., ._ &.. - I> . ._,_, .T._,'-.'. "i I .... .... ,-----_Z'/'_-,..,d.,_../.,,#_..:.:,..._"t_" " _....' U- ..--..v'_r_,re.:.'). - • • •-0.04 ' .'.. '." " " t . .DETECTOR ALIGNMENT-0.08Though great care was taken in the con-struction of the SVX s to keep the maximum -o.,2 "construction error to a minimum, the detectorneeds careful alignment if the design spatial -.o -ao -2o -,o o ,o aO ZaO.._t.._..'°resolution of 12 Izm is to be achieved. Two ,,_=,,y.,,..a,,t,b_,,,types of alignment have been performed sofar: first the alignment of each individual bar-rel to the CTC (global alignment) and then Figure 3. Beam line profile from the two SVX barrels.the internal alignment of the ladders withineach barrel. We took great care in develop- ing is the relative rotation around z, which ising; an alignment technique which concentrates determined by optimizing the match betweenthe. effect of the CTC systematics only in the the CTC track extrapolation to the SVX andglobal alignment step, where a lower accuracy the location of the SVX hits. As a check of theis needed, quality of this procedure an independent fit ofThe global alignment method relies on the the beam line is performed for the two barrelsassumptions that both SVX barrels and the using tracks fully contained in either barrel,CTC must see the beam line in the same spot after applying the alignment corrections. Theresults so far differ by _,15 /_m between theduring a given run, and that each barrel cantwo barrels. Figure 3 shows the distributionbe treated as a rigid body. 5 Mignment param-eters must be determined for each barrel since of the x versus z of the primary vertex as ob-the SVX does not measure z, the longi'audinM tained from this test and the fits performed forcoordinate. These parameters are 3 rotations each barrel.and x and y displacements. The beamline po- A great care was put, during construction,sition as a function of z is calculated first us- in building the SVX to a high level of mechan-ing CTC tracks and then using tracks crossing icM accuracy. In addition, the misalignmentsonly one barrel at a time. The difference in the have been measured with optical methods dur-beamline positions determines the transverse ing assembly and these constants are alreadydisplacements and 2 rotation angles between used for the track reconstruction. This givesthe SVX and the CTC (the latter being used us a very good starting point for the deter-as a reference). The last parameter remain- mination of the internal alignments using theSVX Residuals before and after internal alignmenta--or_i clusteri_c_ B ta_g,e_g olgoritme'_0.2 , t , 1 i2000._ Beforeo = 18.6_m E 7 lal/s,gr_m<3 -iI "1600 L °< tF, oo " .... ' ----k-I O.O ......, <0.aoo, -_ "1-o. _ -- "-_D,*00, -o.= .... I ..... I , , , tO. o z ,, e-0.010 -0.005 0.000 0.005 0.010 _; . AZIUUTH (ema)cmFigure 4. SVX residuals before and after internal Figure 5. Typical event showing secondary vertex ac-alignment corrections, tivlty.crossing wedge boundaries. Also the proce-data and allows some useful simplifications of dure needs to be iterated to stabilize the cor-the process. Some preliminary work has been relations, however small, between the globaldone on internal alignment using tracks, and, and internal alignment procedures. In figure 4though incomplete, it has already produced we show how the track residuals in the SVXsome good results.The method used istofirst improve afterthe internalalignmentconstantsidentify the degrees of freedom which most af- are applied. The width of the residual dis-fect the resolution, to reduce the number of tribution improves from 18.6 _m to 13.6 ;zm.parameters to determine to a minimum. For The width of this residual distribution corre-each ladder we justfitthe followingparam- sponds to a detectorspatialresolutionof 17eters"a translationpara/Iclto the detector/_m, as verified with a simple toy Montecarlo.plane and perpendicular tothe strip direction,and a rotation around the axis perpendica- CONCLUSIONSlar to the detector plane. To cope with theintrinsic degeneracy of the problem, we hold In conclusion the SVX is already perform-: the outermost layer fixed and impose the con- ing very close to the design expectations, andstraintof the average beam line. We then improvements are stillpossible. We have: litthe misalignment parameters on a wedge- searchedsome fractionof our latestjettrig-, by-wedge basis. Wedge-to-wedge corrections gcr data for indications of secondary vertexstill remain to be studied, due to the large activity, and found, through a selection basedstatistics needed, since one has to select tracks only on the SVX, several candidates. Figure 5........... .. .. ,,__,,,,,-w,-_.,-ql.c,_ . , c_,:1shows an example of two back-to-back vertices, Results", in Conference Record of the 1991 "Ieach of multiplicity 3. In this figure we plot, IEEE Nucl. Sci. Syrup., 1991, p. 475.for each track in the event, the impact parame- 8. B. Barnett, et al., "Progress in the Con-ter with respect to the reconstructed primary struction of the CDF Silicon Vertex Detec-vertex versus the angle of the track with re- tor", Nucl. [nstrum. Methods A315, p. 125spect to thex axis, ¢0. Tracks originating from (1992).a common vertex appear aligned in this plot,their intersection with the ¢0 axis being the 9. F. Bedeschi, et al., "SVX Test Beamdecaying particle direction. Tracks from the Results", ;Nucl. Instrum. Methods A315,primary vertex lie on the ¢0 axis. While much p. 188 (1992).work and statistics are still needed to demon- 10. S. A. Kleinfelder, et al., "A Flexible 128strate that we are indeed observing heavy Channel Silicon Strip Detector Instru-flavoured particle decays, the quality of events mentation Integrated Circuit with Sparselike this makes us believe that the SVX will Data Readout", IEEE Trans. on Nucl.play a very important role in the study of Sci. NS-35, p. 171 (1988).heavy flavour physics from the data collected 11. C. Haber, et al., "Design and progotyp-during this period at CDF. ing of the Front End Readout Systemfor the CDF Silicon Vertex Detector",REFERENCES IEEE Trans. on Nucl. Sci. NS-37, p. 11201. F. Abe, et ai., "The CDF Detector: An (1990).Overview", Nucl. Instrurn. Methods A271, i2. S. M. Tkaczyk, et al., "Commissioning ofp. 387 (1988). the Control and Data Acquisition Elec-2. F. Bedeschi, et al., "A Silicon Vertex De- tronics for the CDF Silicon Vertex De-tector for CDF", IEEE Trans. on Nucl. rector", in Conference Record of the i99ISci. NS-33, p. 140 (1985). IEEE Nucl. Sci. Syrup., 1991, p. 753.3. F. Bedeschi, et al., "CDF Silicon Detec- 13. K. J. Turner, et al., "Control and Data Ac-tor Prototype Test Beam Results", IEEE quisition Electronics for the CDF SiliconTrans. on Nucl. Sci. NS-36, p. 35 (1989). Vertex Detector", in Conference Reco','d of4. C. Haber, "The CDF Silicon Microstrip the I99i IEEE Nucl. Sci. Syrnp., 1991;Vertex Detector", in Proceedings of p. 888.the 7°` Topical Workshop on Proton-Antiproton Collider Physics, 1989, p. 443.5. W. C. Carithers, et al., "The CDF SVX:A Silicon Vertex Detector for a HadronCollider", Nucl. Instrurn. Methods A289,p. 388 (1990).6. J. Skarha, et ai, "Construction of the CDFSilicon Vertex Detector", in ConferenceRecord of the I991 IEEE Nucl. Sci. Sym;,.,1991, p. 426.7. W. C. Carithers, et at, "The CDF SiliconVertex Detector: An Overview and Tes't

Operation of the CDF Silicon Vertex Detector with Colliding Beams at Fermilab

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Operation of the CDF silicon vertex detector with colliding beams at Fermilab

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Operation of the CDF silicon vertex detector with colliding beams at Fermilab

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